The Nigerian military reported fresh fighting with Boko Haram insurgents on Monday, a day after the group seized an army barracks in northeastern Borno state and attacked the state capital, Maiduguri.

Defense spokesman General Chris Olukolade told VOA that an "operation involving air and land assets is underway" to retake the barracks in Monguno, about 180 kilometers northwest of Maiduguri.

Towns of Monguno and Konduga, in Borna state, Nigeria

Also, the army said on Twitter that troops battled militants Sunday night and early Monday in Konduga, a town about 25 kilometers southeast of Maiduguri.

The military said "ground troops are in charge" of the area and "substantial amounts of heavy weapons" have been captured. It said both sides suffered casualties.

Reuters news agency reported that local journalist Bello Dukku counted more than 100 bodies of people killed in Sunday's fighting at a morgue in Maiduguri. Dukku said the dead included at least 15 soldiers and a few civilians.

On Sunday, Nigerian officials said soldiers repelled three separate attempts by insurgents to enter Maiduguri.

A security officer said each attempt was from a different direction. Authorities barricaded the roads and imposed a curfew in the city until further notice.

The northeastern city of Maiduguri, birthplace of Boko Haram's five-year-old insurgency, is the town it covets as the potential capital of an Islamic state.

Attack on Monguno

Militants also hit two other towns Sunday, including Monguno, which lies on the shores of Lake Chad.

A defense spokesman said on Sunday evening that airstrikes had been carried out to take back the town after ground troops were forced to retreat.

"The operation resumed on Monguno this morning through air bombardment to dislodge the insurgents," a security source said on Monday.

At least 15 soldiers were killed along with more than over 25 civilians in the town on Monday, a source said.

Soldiers in Monguno said on Sunday they had fled because of the insurgents' superior fire power.

Monguno lies near the larger town of Baga, where a military base was taken over by Boko Haram in early January in an attack that left scores of civilians dead.

In a subsequent video, the insurgents claimed responsibility for the capture of Baga and said they had seized enough weapons to "annihilate Nigeria."

The conflict has intensified in the past year and the government's handling of the security situation is major issue in the campaign for a presidential election on February 14, which pits President Goodluck Jonathan against former military ruler Muhammadu Buhari.

In a visit to Nigeria on Sunday, U.S. Secretary of State John Kerry said the United States was committed to helping Nigeria fight Boko Haram, but its ability to do so would hinge on how the well election is conducted.

Boko Haram has killed thousands of people since launching its insurgency in 2009 and now controls large parts of Borno state.